反应显示子组件值的总和不准确

Posted 2023-02-22

【中文标题】反应显示子组件值的总和不准确

【英文标题】：React displaying sum of child components values not accurate

【发布时间】：2018-12-03 03:57:16

【问题描述】：

我试图显示所有子组件列表值的总和，但它不准确，因为它也保留了数组中的前一个值，我该如何解决这个问题？

代码：

import React from 'react';
import styled from 'styled-components';

const Container = styled.div `
  display: flex;
  flex-direction: row;
  justify-content: space-between;
`;

class ShoppingList extends React.Component 
  state = 
    questions: [''],
    sum: 0
  

  handleText = i => e => 
    console.log('id', this.state.id);
    let questions = [...this.state.questions];
    questions[i] = parseInt(e.target.value);
    if (questions.length === 1 && isNaN(questions[0])) 
      questions[0] = ''
    
    let sum = questions.reduce(function(a, b) 
      if (isNaN(a)) 
        a = '';
      
      if (isNaN(b)) 
        b = '';
      
      return a + b;
    );
    console.log('sum', sum);
    this.props.value(sum);
    this.setState(
      questions,
      sum
    )
  

  addExpense = e => 
    e.preventDefault()
    let questions = this.state.questions.concat([''])
    this.setState(
      questions
    )
  

  render() 
    return (
      <div>
        <Container>
          <select>
            <option value="food">Food</option>
            <option value="houseware">Houseware</option>
            <option value="entertainment">Entertainment</option>
          </select>
          <button onClick=this.addExpense>Add expense</button>
        </Container>
        this.state.questions.map((question, index) => (
          <Container  key=index>
            <input
              type="text"
            />
            <input
              type="number"
              onChange=this.handleText(index)
              value=question
            />
          </Container>
        ))
        <Container>
          <label>Total:</label>
          <label>this.state.sum ? this.state.sum + ' €' : 0 + ' €'</label>
        </Container>
      </div>
    )
  


export default ShoppingList;

和：

import React from 'react';
import styled from 'styled-components';
import ShoppingList2 from './ShoppingList2';

const Container = styled.div `
  position:absolute;
  left:0;
  bottom:0;
  right:0;
  display: flex;
  flex-direction: row;
  justify-content: space-between;
`;

class TotalPrice extends React.Component 
  state = 
    shoppingLists2: [ShoppingList2],
    shoplistsums: [],
    sum: 0
  

  AddShoppingList = () => 
    let shoppingLists2 = this.state.shoppingLists2.concat(ShoppingList2);
    console.log(shoppingLists2);
    this.setState(
      shoppingLists2
    )
  

  onUpdate = (val) => 
    console.log('val', val);
    let shoplistsums = this.state.shoplistsums.concat(val);
    let sum = shoplistsums.reduce(function(a, b) 
      return a + b;
    );
    this.setState(
      shoplistsums,
      sum
    )
  

  render() 
    return (
      <div>
        this.state.shoppingLists2.map((ShoppingList2, index)=>(
          <ShoppingList2
            key=index
            value=this.onUpdate
          />
        ))
        <Container>
          <label>Total:</label>
          <label>this.state.sum + ' €'</label>
          <button onClick=this.AddShoppingList>Add Receipt</button>
        </Container>
      </div>
    );
  


export default TotalPrice;

这是它的外观和工作原理以及问题：

我最近才开始使用react，所以如果您有其他建议，请告诉我！

【问题讨论】：

看起来 questions 是一个字符串数组。你如何通过添加一个字符串数组来得到总和？如果问题处于具有问题（字符串）和值（数字）的对象的状态下，那么对于 sum 添加应用程序值（数字）会更好。

问题[i] = parseInt(e.target.value);它在 ShoppingList 中解析

你的设计中应该有什么问题。美食、家居娱乐？还是它们是类别？

【参考方案1】：

已修复，可以查看@-https://github.com/benonymus/timetravel